Re: [PATCH v6 2/3] tpm: vtpm_proxy: Implement request_locality function.

[Stefan Berger]

On 05/24/2017 06:21 PM, Jarkko Sakkinen wrote:
> On Wed, May 24, 2017 at 05:39:40PM -0400, Stefan Berger wrote:
> > Implement the request_locality function. To set the locality on the
> > backend we define vendor-specific TPM 1.2 and TPM 2 ordinals and send
> > a command to the backend to set the locality for the next commands.
> >
> > To avoid recursing into requesting the locality, we set the
> > TPM_TRANSMIT_RAW flag when calling tpm_transmit_cmd. To avoid recursing
> > into TPM 2 space related commands, we set the space parameter to NULL.
> >
> > Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxxxxxxx>
> > ---
> >   drivers/char/tpm/tpm-interface.c  |  1 +
> >   drivers/char/tpm/tpm_vtpm_proxy.c | 36 ++++++++++++++++++++++++++++++++++++
> >   include/uapi/linux/vtpm_proxy.h   |  4 ++++
> >   3 files changed, 41 insertions(+)
> >
> > diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> > index 2eacda2..876d45f 100644
> > --- a/drivers/char/tpm/tpm-interface.c
> > +++ b/drivers/char/tpm/tpm-interface.c
> > @@ -537,6 +537,7 @@ ssize_t tpm_transmit_cmd(struct tpm_chip *chip, struct tpm_space *space,
> >   
> >   	return 0;
> >   }
> > +EXPORT_SYMBOL_GPL(tpm_transmit_cmd);
> >   
> >   #define TPM_DIGEST_SIZE 20
> >   #define TPM_RET_CODE_IDX 6
> > diff --git a/drivers/char/tpm/tpm_vtpm_proxy.c b/drivers/char/tpm/tpm_vtpm_proxy.c
> > index 751059d..66024bf 100644
> > --- a/drivers/char/tpm/tpm_vtpm_proxy.c
> > +++ b/drivers/char/tpm/tpm_vtpm_proxy.c
> > @@ -371,6 +371,41 @@ static bool vtpm_proxy_tpm_req_canceled(struct tpm_chip  *chip, u8 status)
> >   	return ret;
> >   }
> >   
> > +static int vtpm_proxy_request_locality(struct tpm_chip *chip, int locality)
> > +{
> > +	struct tpm_buf buf;
> > +	int rc;
> > +	const struct tpm_output_header *header;
> > +
> > +	if (chip->flags & TPM_CHIP_FLAG_TPM2)
> > +		rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS,
> > +				  TPM2_CC_SET_LOCALITY);
> I would always go with this branch.
>
> > +	else
> > +		rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND,
> > +				  TPM_ORD_SET_LOCALITY);
> > +	if (rc)
> > +		return rc;
> > +	tpm_buf_append_u8(&buf, locality);
> > +
> > +	rc = tpm_transmit_cmd(chip, NULL, buf.data, tpm_buf_length(&buf), 0,
> > +			      TPM_TRANSMIT_UNLOCKED | TPM_TRANSMIT_RAW,
> > +			      "attempting to set locality");
> > +	if (rc < 0) {
> > +		locality = rc;
> > +		goto out;
> > +	}
> > +
> > +	header = (const struct tpm_output_header *)buf.data;
> > +	rc = be32_to_cpu(header->return_code);
> > +	if (rc)
> > +		locality = -1;
> > +
> > +out:
> > +	tpm_buf_destroy(&buf);
> > +
> > +	return locality;
> > +}
> > +
> >   static const struct tpm_class_ops vtpm_proxy_tpm_ops = {
> >   	.flags = TPM_OPS_AUTO_STARTUP,
> >   	.recv = vtpm_proxy_tpm_op_recv,
> > @@ -380,6 +415,7 @@ static const struct tpm_class_ops vtpm_proxy_tpm_ops = {
> >   	.req_complete_mask = VTPM_PROXY_REQ_COMPLETE_FLAG,
> >   	.req_complete_val = VTPM_PROXY_REQ_COMPLETE_FLAG,
> >   	.req_canceled = vtpm_proxy_tpm_req_canceled,
> > +	.request_locality = vtpm_proxy_request_locality,
> >   };
> >   
> >   /*
> > diff --git a/include/uapi/linux/vtpm_proxy.h b/include/uapi/linux/vtpm_proxy.h
> > index a69e991..58ac73c 100644
> > --- a/include/uapi/linux/vtpm_proxy.h
> > +++ b/include/uapi/linux/vtpm_proxy.h
> > @@ -46,4 +46,8 @@ struct vtpm_proxy_new_dev {
> >   
> >   #define VTPM_PROXY_IOC_NEW_DEV	_IOWR(0xa1, 0x00, struct vtpm_proxy_new_dev)
> >   
> > +/* vendor specific commands to set locality */
> > +#define TPM2_CC_SET_LOCALITY	0x20001000
> > +#define TPM_ORD_SET_LOCALITY	0x20001000
> > +
> >   #endif /* _UAPI_LINUX_VTPM_PROXY_H */
> > --
> > 2.4.3
> What practical benefit you get from these two constants? I understand
> the value range but not so much the redundant code.

If you want to change this, please go ahead and give it a sinle name.
For the code branches above I think that we should at least send a TPM 
1.2 formatted command in case of TPM 1.2 and a TPM 2 formatted one in 
case of TPM 2. It seems just 'proper.'

   Stefan